Hi Julie
You haven't said which benefit you are talking about. If you select the appropriate benefit from the Guides tab at the top of the page, the first guides for PIP or for ESA/UC have sections about telephone assessments, what to expect, and the types of questions you may be asked. You'd be wise to read through that guidance.
Once you've had a look, if you have any specific questions, come back and ask and we will try and help.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems